1. Field of the Invention
The invention relates to a device for the heat treatment of bulk material, such as a dryer or a cooling or heating apparatus.
2. Description of the Prior Art
Bulb material dryers are known which have a drum-shaped container with a horizontal longitudinal axis, in which there is centrally mounted a driven shaft which is provided with mixing tools on radial arms, and in which discs are arranged on the shaft concentric to the container which can be heated through the shaft and which rotate with it. These discs have the disadvantage that the dryer is practically inaccessible for servicing operations. Repairs to the heatable discs can only be conducted if the shaft together with the heating elements mounted upon it, namely the discs is removed from the container. The available heating surface cannot in practice be altered, because with simple means it is not possible to change the number of heating discs, i.e. to incorporate additional heating discs or to remove a few of the heating discs. Moreover the temperature of the heating discs cannot regulated individually, so that there is a danger, especially with a continuously operated dryer that when the drying is almost complete products will be overheated and will thus suffer damage. Furthermore the disc-shaped heating elements rotating with the shaft prevent the incorporation of further mixing elements, such as cutter heads, in the region of the rotating discs on the wall of the container.
In order to remove vapours or other moisture released from the bulk material gas flows axially through the dryer container. In the case of long large dryers such high flow rates are generated that product particles are entrained in the flow and so the moisture-removing gas must be passed through a separator. In addition the gas temperature cannot be adjusted over the length of the dryer to suit requirements and cannot be adapted to the requirements of the particular product.